rpi: Conditionally add simple-framebuffer node

It appears that RPi firmware has already added framebuffer
node under /chosen, at least on RPi 2 versions. So check
for this and don't add duplicate node.

Signed-off-by: Ivan T. Ivanov <iivanov@suse.de>
Signed-off-by: Matthias Brugger <mbrugger@suse.com>
diff --git a/board/raspberrypi/rpi/rpi.c b/board/raspberrypi/rpi/rpi.c
index df52a46..372b26b 100644
--- a/board/raspberrypi/rpi/rpi.c
+++ b/board/raspberrypi/rpi/rpi.c
@@ -497,12 +497,11 @@
 
 int ft_board_setup(void *blob, struct bd_info *bd)
 {
-	/*
-	 * For now, we simply always add the simplefb DT node. Later, we
-	 * should be more intelligent, and e.g. only do this if no enabled DT
-	 * node exists for the "real" graphics driver.
-	 */
-	lcd_dt_simplefb_add_node(blob);
+	int node;
+
+	node = fdt_node_offset_by_compatible(blob, -1, "simple-framebuffer");
+	if (node < 0)
+		lcd_dt_simplefb_add_node(blob);
 
 #ifdef CONFIG_EFI_LOADER
 	/* Reserve the spin table */